A high-pressure discharge lamp used as a light source for a projector is hot immediately after being extinguished. The pressure on the inside of the lamp is high. In general, the high-pressure discharge lamp does not easily discharge in a high-pressure state. Even if an attempt is made to relight the high-pressure discharge lamp in the high-pressure state immediately after being extinguished, the high-pressure discharge lamp cannot sometimes lit. If a voltage is applied to the high-pressure discharge lamp a plurality of times in order to light the high-pressure discharge lamp in such a state, it is likely that electrodes of the high-pressure discharge lamp will deteriorate.
Examples of a method of preventing failure in relighting the high-pressure discharge lamp include ensuring that an extinguishing period during which the discharge lamp is switched off is sufficiently long such that the internal pressure of the high-pressure discharge lamp decreases and the high-pressure discharge lamp is cooled to temperature suitable for discharge. In this case, if the extinguishing period during which the high pressure discharge lamp is turned off is too long, there will be an increase in the amount of delay until a user can use the projector and a deterioration in the convenience of use.
In order to reduce the extinguishing period during which the high pressure discharge lamp is switched off, a projector is also proposed that includes a cooling mechanism such as a fan or a Peltier element to cool the high-pressure discharge lamp.
A technique for determining a cooling time for causing the cooling mechanism to operate is disclosed in Patent Literature 1. In a projector disclosed in Patent Literature 1, a cooling time set in advance according to an extinguishing time is used. The length of the cooling time is set according to how short is the time required to extinguish the lamp. The longer the amount of time required to extinguish the lamp, the shorter is the cooling time that is set.